Apparatus for pumping concrete and other bulk materials are well known. For example, U.S. Pat. No. 6,299,416 to Kwag discloses a pump device that includes a pair of hydraulic drive cylinders. Each cylinder includes an axial bore and a drive piston coupled to a piston rod that is able to slide within the respective bore, thereby dividing the bore into a head chamber and a base chamber. Fluid lines connect the base chamber of each cylinder to an oil pump and the head chambers of the cylinders to each other.
Oil is pumped in one direction from the pump into the base chamber of a first of the cylinders, thereby retracting the first piston and rod into the first cylinder. This causes oil to be pushed out of the first cylinder's head chamber, through a fluid line into the head chamber of the second cylinder, thereby advancing the second piston and rod outwardly from the second cylinder. Oil in the base chamber of the second cylinder is returned to the pump as the second piston and rod are advanced from the second cylinder.
The pump is then reversed, thereby pumping oil into the base chamber of the second cylinder to retract the second piston and rod this causes the oil in the head chamber of the second cylinder to be transferred into the head chamber of the first cylinder, thereby advancing the first piston and rod, and returning oil in the base chamber of the first cylinder to the pump. The Kwag patent explains that this reciprocating process may be repeated to drive cylinders or other mechanisms to pump concrete from a hopper into a conduit for delivery to a location where the concrete is to be poured.
This method of alternately pumping fluid into the base chambers of a pair of cooperating hydraulic cylinders is known as “rod side operation.” Such arrangements are often used when it is desired to deliver relative high volumes of concrete or other materials at relative low pressures.
In addition, pumping devices designed for “head side operation” are also known. These systems alternately pump fluid into the head chambers of a pair of hydraulic cylinders with the base chambers being connected together by a fluid line. Head side operation is generally used to pump relatively lower volumes at higher pressures.
Accordingly, apparatus and methods for pumping concrete and other flowable materials would be useful.